As our systems become more distributed and more connected, security has never been more important. The catalog of known exploits is vast. There are more vulnerabilities and pitfalls than any expert can understand. And yet, security is so important that it can not be left to experts.

Fortunately, all good practices flow from a small set of principles. These principles should be known by every programmer and every manager.

Computers are machines that manipulate numbers. That is literally all that they can do, and yet they are now facilitating and mediating virtually all human activity. This is the story of numbers: where they came from, how they work, and where they may be going. Every programmer should know this story.

This is the story of the representation of text as numbers. We will range from the earliest codes, Hollerith and Morse, to what will likely be the last character code, Unicode. The mysterious control codes of ASCII will be explained. Subtle decisions made in the last century had large unintended consequences. The irritating eternal dilemma "Tabs or Spaces?" will finally be resolved logically for the first time.